Engines, for example vehicle engines, are being downsized and boosted, which is reducing the available vacuum from the engine. This vacuum has many potential uses, including use by the vehicle brake booster.
One solution to this vacuum shortfall is to install a vacuum pump. Vacuum pumps, however, have a significant cost and weight penalty to the engine, their electric power consumption can require additional alternator capacity, and their inefficiency can hinder fuel economy improvement actions.
Another solution is using aspirators that generate vacuum by creating an engine air flow path that is parallel to the throttle, referred to as an intake leak. This leak flow passes through a Venturi that generates a suction vacuum. The problem with presently available aspirators is that they are limited in the amount of vacuum mass flow rate they can generate and by the amount of engine air they consume.
A separate vacuum source may be required to operate vehicle systems while the engine is either under boost or operating with an inadequate amount of manifold vacuum. A need exists for improved designs that include fewer parts and/or fewer components to generate vacuum when supplied with boost and also when supplied with manifold vacuum.